When a guy checks a girl out?

I went to a restaurant earlier today and I noticed this guy kept looking at my face as I was heading in his direction for a couple of seconds. Then later, I saw him look at some other people and then he looks back at me from head to toe-he was literally scanning my body. After he was done, he kept looking at the floor/ground like he was thinking about something. Now, was the way he was checking me out a good or a bad thing?